(+)-(S)-4-[4-[(4-Chlorophenyl)(2-pyridyl)methoxy]piperidino]butyric acid and a pharmacologically acceptable acid addition salt thereof have an antihistaminic action and an antiallergic action. They are also characterized in that secondary effects such as stimulation or suppression of the central nerve often seen in the case of conventional antihistaminic agents can be minimized, and can be used as effective pharmaceutical agents for the treatment of human and animals (JP-B-5-33953, JP-A-2000-198784).
Particularly, a tablet comprising (+)-(S)-4-[4-[(4-chlorophenyl)(2-pyridyl)methoxy]piperidino]butyric acid monobenzenesulfonate (general name: bepotastine besilate) has been already marketed as a therapeutic agent for allergic rhinitis and itching associated with hives and dermatoses.
On the other hand, (+)-(S)-4-[4-[(4-chlorophenyl)(2-pyridyl)methoxy]piperidino]butyric acid and a pharmacologically acceptable acid addition salt thereof are unstable to light in an aqueous solution, and colored or precipitated with the lapse of time, which has made the use thereof as an aqueous liquid preparation difficult. In the case of an aqueous liquid preparation such as an eye drop and a nasal drop, a method comprising blocking light by preserving in a light-shielding container and the like can be used, but complete light-shielding is practically difficult. Thus, stabilization of an aqueous liquid preparation itself as a preparation is desirable. As a method of light-stabilizing an eye drop, a U.S. Pat. No. 2,929,274 discloses a method comprising adding boric acid and/or borax and glycerin, but according to this method, stabilization of (+)-(S)-4-[4-[(4-chlorophenyl)(2-pyridyl)methoxy]piperidino]butyric acid and a pharmacologically acceptable acid addition salt thereof to light was not observed. As a general stabilization method, a method comprising placing in the coexistence of an antioxidant such as BHT etc., and the like are known (JP-A-7-304670).